1. Field of the Invention
The present invention relates to an oxide superconductor which exhibits excellent superconducting properties such as a high critical current density. Further, the present invention is applicable to, for example, a current lead, magnetic bearing, a magnetic shielding and to a bulk magnet.
2. Description of the Related Art
Hitherto, there has been known a conventional method of manufacturing such a kind of an oxide superconductor (see Japanese Examined Patent Publication No. Hei 7-51463/1995 Official Gazette), by which a RE--Ba--Cu--O oxide superconductor (incidentally, RE is a rare earth element including Y) is manufactured by performing a treatment on a raw material mixture containing a RE compound, Ba compound and a Cu compound (incidentally, this treatment includes at least a burning (or baking) process to be performed in a range of temperatures that are higher than the melting point of such a raw material mixture).
In the case of this conventional manufacturing method, the raw material mixture, in which the RE compound, the Ba compound and the Cu compound are mixed in a predetermined mole ratio, is once melted. Thereafter, the raw material mixture is quenched and solidified. Then, the solidified raw material mixture is pulverized or crushed into fine powder. Subsequently, such powder is heated again to a temperature of a high temperature region in which the powdery mixture partially presents a liquid phase. Thereafter, the mixture is gradually cooled. Thus, a superconducting phase is grown. Furthermore, an oxide superconductor exhibiting a relatively high critical current density can be obtained by performing annealing process in an oxygen atmosphere.
However, in the case of the aforementioned manufacturing method, the coagulation and condensing of the raw materials occur when once melting the raw material mixture for forming a RE--Ba--Cu--O superconductor. Thus, it is necessary for uniformly dispersing the raw materials to crush the raw materials into very fine powder. Moreover, the density of a sample (or specimen), which is melted and recrystallized by using fine raw materials, becomes very high. Thus, the conventional method has problems in that the diffusion velocity of oxygen is low and that an oxygen annealing time is very long.
The present invention is accomplished to solve the aforementioned problems of the prior art.